I. Field of the Invention
The present invention relates generally to motorized concrete finishing trowels. More particularly, the present invention relates to motor powered riding trowels of the type classified in United States Patent Class 404, Subclass 112.
II. Description of the Prior Art
It has long been recognized by those skilled in the art that freshly placed concrete must be appropriately finished. Motorized riding trowels can fine finish plastic concrete on very large floor jobs soon after pouring. Motorized riding trowels have proven themselves in the industry. Their effectiveness for quickly and efficiently finishing large surfaces of wet concrete with either revolving blades or pans is undeniable, and such trowels are rapidly becoming the industry standard.
A typical power riding trowel comprises two or more bladed rotors that project downwardly and frictionally contact the concrete surface for finishing. These rotors are driven by one or more self contained motors mounted on the frame. The motors are linked to rotor gearboxes to revolve the rotors. The riding trowel operator sits on top of the frame and controls trowel movement with a steering system that tilts the axis of rotation of the rotors. The weight of the trowel and the operator is transmitted frictionally to the concrete by the revolving blades. The unbalanced frictional forces caused by rotor tilting enable the trowel to be steered.
As the freshly poured concrete "sets", it soon becomes hard enough to support the weight of the specialized finishing trowel. While concrete is still "green" (i.e., within one to several hours after pouring depending upon the concrete mixture involved), power trowel pan finishing is required. Soon after panning, trowelling with power blades may begin as the slab adequately hardens. Numerous concrete finishing machines are known in the art for these purposes. Proper and timely finishing insures that desired surface characteristics including smoothness and flatness are achieved.
Power riding trowels should be passed over the surface being treated several times as the concrete sets. It is recommended that finishing pans be used first, when the concrete is relatively green, to achieve "super-flat" and "super-smooth" floors. The advent of more stringent concrete surface finish specifications using "F" numbers to specify flatness (ff) and levelness (fl), dictates the use of pans on a widespread basis. Pan finishing is normally followed by high speed blade finishing, after the pans are removed from the rotor blades. The trowel blades are adjusted to a relatively high pitch angle, and they directly frictionally contact the concrete surface. Rotors operate at high speed, in excess of one hundred-fifty RPM or more, resulting in a smooth, slick surface. High power riding trowels that quickly and efficiently finish large surfaces of wet concrete with either revolving blades or pans are rapidly becoming the industry standard.
Holz, in U.S. Pat. No. 4,046,484 shows a twin rotor riding trowel. U.S. Pat. No. 3,936,212, also issued to Holz, shows a three rotor riding trowel powered by a single motor. Although the designs depicted in the latter two Holz patents were pioneers in the riding trowel arts, the devices were difficult to steer and control.
Prior U.S. Pat. No. 5,108,220 owned by Allen Engineering Corporation, the same assignee as in this case, relates to an improved, fast steering system for riding trowels. Its steering system enhances riding trowel maneuverability and control. The latter fast steering riding trowel is also the subject of U.S. Des. Pat. No. 323,510 owned by Allen Engineering Corporation.
Allen Engineering Corporation U.S. Pat. No. 5,613,801 issued Mar. 25, 1997 discloses a power riding trowel equipped with twin motors. The latter design employs a separate motor to power each rotor. Steering is accomplished with structure similar to that depicted in U.S. Pat. No. 5,108,220 previously discussed.
Allen U.S. Pat. No. 5,480,257 depicts a twin engine powered riding trowel whose guard structure is equipped with an obstruction clearance system. When troweling areas characterized by projecting hazards such as pipes or ducts, or when it is necessary to trowel hard-to-reach areas adjacent walls or the like, the guard clearance structure may be retracted to apply the blades closer to the target region.
Allen U.S. Pat. No. 5,685,667 depicts a twin engine riding trowel using "contra rotation." For enhanced stability and steering, the rotors rotate in a direction opposite from that normally expected in the art.
Although large, high power trowels are respected for their speed, horsepower, and efficiency, there are other considerations that deserve attention. For example, modern high power trowels require periodic maintenance and inspection. Easy access to critical parts is desirable. Downtime can be minimized by proper design that eases mechanical service requirements. Those parts that are most likely to require service from time to time should be easily accessed. At the same time, ease of access should not denigrate safety consideration. Very hot parts, for example, should be shrouded properly to prevent burns. (And adequate airflow must be established for proper cooling.) Besides service efficiency, operator comfort must be a paramount design goal.
With extremely large pours, troweling (i.e., panning) may begin soon after placement, continuing to late in the evening. Very large jobs may require two or more riding trowels, as critical finishing should ideally be completed before the concrete reaches a predetermined hardness. Thus the work hours may be long, and operator comfort must be insured. While operating a typical riding trowel the operator is obviously exposed to vibration, noises, and heat. The operator needs a comfortable, adjustable seat. Ideally, the seat is readily accessible to the controls. Further, the seat, and the platform mounting the seat, should be designed to dissipate the considerable heat generated by the high power trowel engines. In multiple engine designs airflow and cooling considerations are even more important. An ideal arrangement is obtained by combining the operator seat supporting structure with a ventilation pathway capable of readily dissipating engine exhaust heat. While the support structure preserves operator comfort and promotes safety, it may be relatively quickly released and deflected out-of-the way to expose critical trowel parts for service.